Method of forming projections in reed switch assemblies by selective heat softening



Feb. 20, 1968 J. KUTYLA METHOD OF FORMING PROJECTIONS IN REED SWITCH ASSEMBLIES BY SELECTIVE HEAT SOFTENING Filed Oct. 28, 1963 4. 2% MW@ W W United States Patent 3,359,382 Patented Feb. 20, 1968 METHOD OF FORMING PROJECTIQNS IN REED SWITCH ASSEMBLIES BY SELECTIVE HEAT SOFTENING John Kutyla, Chicago, Ill., assignor to C. P. Clare & Company, Chicago, 11]., a corporation of Delaware Filed Oct. 28, 1963, Ser. No. 319,457 9 Claims. Cl. 65-110) ABSTRACT OF THE DISCLOSURE A method of forming magnetic reed damping projections in the glass housing of a sealed magnetic reed switch in which a dot of an infra-red absorbing material, such as a colloidal graphite dispersion in water, is placed on the outside wall of the housing at a point adjacent a magnetic reed. The housing is then subjected to infra-red radiation which is absorbed by the material to heat a localized area of the housing. When the heated area becomes sufficiently softened, it is displaced inwardly by the differential in pressure across the housing to form the damping projection.

This invention relates to an improved switching matrix using sealed switches and, more particularly, to a method of making sealed switches.

One type of matrix' circuit commonly used in switching and decoding networks includes a plurality of scaled magnetic switches containing two magnetic reeds or elements that are moved into engagement by an applied magnetic field of a given strength. In many of these circuits, such as the one shown in the copending application of Wyman L. Dee g, Ser. No. 228,836, filed Oct. 8, 1962, now United States Patent No. 3,183,487, the necessary operating flux for each sealed switch is provided by a two coil winding having one coil disposed generally around one of the magnetic elements and the other coil disposed around the remaining element. The two coils of the switch winding are connected to the rows and columns of a two coordinate matrix network so that the application of an operating signal to one of the column inputs and to one of the row inputs energizes both of the coils in Only a single one of the sealed switches so that only this switch or cross-point is operated to a closed condition. When a given one of the switches has been closed, it can be retained in a closed condition by maintaining the energization of only one of the two coils in the winding.

There is a problem associated with the use of these reed switches in a matrix which tends to limit their use fulness. When both of the input signals to the winding of a closed switch or cross-point are removed, the switch opens. The magnetic reeds, after release, tend to oscillate about their normally open position for a considerable length of time. During this period of oscillation, the gap between the reeds becomes alternately wider and narrower than normal. This means that the ampere-turns or the strength of the input signal required to close or operate the switch is alternately greater and less than normal. Therefore, if one of the coils in the winding associated with a switch in an oscillatory state is energized with a normal input signal during the period of oscillation in which the magnetic reeds are positioned more closely adjacent each other, the switch can reclose to provide an inadvertently closed cross-point in the matrix. This closure from only a single row or column input results in false matrix operation.

A period of from ten to fifty milliseconds is often required for the reed oscillations to be damped so that a new signal input to the matrix can safely be applied. This time delay reduces the operating frequency of the circuit of which the matrix forms a part. If a signal input could be immediately reapplied after the release of each switch or cross-point, a more desirable operating rate could be achieved.

Accordingly, one object of this invention is to provide a new and improved switching matrix.

Another object of this invention is to provide a switching matrix capable of high speed repetitive operation.

Another object is to provide a matrix circuit using sealed switches in which oscillation of the flexible magnetic reeds in the switch is prevented.

A further object is to provide a method of making sealed switches in which oscillation of the flexible magnetic elements in the switch is damped.

Another object is to provide a method of integrally forming reed damping projections within the glass housing of a sealed switch.

A further object is to provide a method of integrally forming reed damping projections or depressions in the glass housing of a sealed switch by applying heat absorbing material to a selected area on the housing and subjecting the switch to heat.

Another object is to provide a method of forming reed engaging depressions in a sealed magnetic switch by applying infra-red absorbing material to the glass housing of the switch in the areas in which the depressions are to be formed and then subjecting the switch to infra-red radiation. I

In accordance with these and many other objects, an embodiment of the'present invention comprises a switching matrix comprising a plurality of sealed magnetic switches containing two magnetic reeds with overlapping end portions that are moved into engagement by the application of a magnetic field of a given strength. Each of the sealed switches is provided with an operating winding containing two spaced coils encircling the magnetic reeds. The two coils in each winding are connected in rows and columns to provide, for instance, a two coordinate input matrix circuit adapted to receive row and column input signals. A selected sealed switch or crosspoint is closed by concurrently energizing both coils of the operating winding of the selected switch.

In prior matrix circuits using sealed switches, the release of the cross-point by terminating the energization of one or both of the coils associated with the operated switch permits the overlapping ends of the magnetic elements to separate. In separating, the free ends of the magnetic reeds tend to oscillate about their normal positions so that, at certain times, the ends of the reeds are disposed closer to each other than in the normal released condition of the switch. If an energizing signal is applied to one of the windings during this interval, it is possible for the switch or cross-point to be reclosed in the absence of energizing signals for both of the coils in the operating winding. In accordance with the present invention, this false operation of the matrix is avoided by forming projecting portions or depressions in the glass of the housing for the switches in positions disposed adjacent the overlapping end portions. When an operated switch in the matrix is released, the free ends of the magnetic reeds strike the depressions or projecting portions of the glass housing so that the reeds cannot swing beyond their normal positions. The impact of the free ends of the reeds on the projecting portions dissipates the kinetic energy in the reeds to prevent oscillation thereof and the possibility of false operation of the matrix.

In accordance with another feature of the present invention these projections or depressions in the glass envelope of the switch are formed in a novel manner. The sealed switch generally comprises an elongated glass or dielectric housing in the opposite ends of which a pair of 3 magnetic reeds or elements are sealed with their inner ends disposed in overlapping relation. To provide means for preventing oscillatory movement of the reeds within the glass housing when the switch is released a dot of material that absorbs infra-red energy is placed on the outer wall of the housing aligned with the free end portion of the reed that is to be engaged by the damping or projecting means. The housing is then subjected to infrared radiation which passes through the glass envelope without causing any appreciable heating thereof. However the dots or bodies of heat absorbing material absorb heat from the infra-red radiation and soften or render plastic the adjacent portions of the glass housing. The interior of the sealed switch is normally at a subatmospheric pressure which cooperates with the weight of the softened glass to cause the plastic or softened portions thereof to move or to be displaced inwardly into the cavity of the glass housing to engage the desired portion of the magnetic element. When the softened or plastic glass touches the reed the metal of the reed serves as a heat sink to remove heat from the plastic glass and to prevent further inward movement thereof. The housing of the switch is then cooled to permit the projections to solidify and the residue of the heat absorbing material is cleaned from the exterior of the glass housing.

Many other objects and embodiments of the present invention will become apparent from considering the following detailed description in conjunction with the drawings in which:

FIG. 1 is a schematic diagram of a switching matrix embodying the present invention;

FIG. 2 is an enlarged sectional view taken along the line 2-2 in FIG. 1 showing one of the sealed switches;

FIG. 3 is a fragmentary sectional view of a conventional sealed switch on which the method embodying the present invention is performed;

FIG. 4 is a fragmentary sectional view similar to FIG. 3 illustrating the application of a heat absorbing material to the housing of the sealed switch;

FIG. .5 illustrates the formation of a depression or projection in the sealed switch in accordance with the present invention; and

FIG. 6 is a fragmentary top plan view taken generally in the direction of line 66 in FIG. 2.

Referring now more specifically to FIG. 1 of the drawor reeds 14 and 16 sealed in the opposite ends of an elongated dielectric or glass housing or envelope 18. Each of the sealed switches 12 is provided with an operating winding including a pair of coils 20 and 22 spaced from each other along the length of the housing 18 and each individually encircling one of the magnetic elements 14 and 16, respectively. Each of the coils 20 and 22 provides a substantially half of the flux necessary to move the overlapping ends 14a and 16a of the magnetic reeds 14 and 16 into engagement to actuate the switch 12 to its closed condition. Thus, both of the coils 20 and 22 in each of the winding means for the switches 12 must be concurrently energized for the associated switch to be operated to a closed condition. However the energization of either one of the coils 20 or 22 will retain a previously actuated switch in a closed condition.

To connect the windings for the sealed switches 12 in the matrix circuit into a matrix network, one terminal of each of the coils 20 and 22 is connected to a source of reference potential, such as ground, and the other terminals of these coils are selectively interconnected with two coordinate inputs to the matrix circuit 10. As an example, the coil 22 on the uppermost switch illustrated in FIG. 1 can be connected to a common row conductor 24 representing, for instance, a digital value 1. The corresponding terminal of the coil 20 can be connected to a 4 common column conductor 26 representing, for instance, the digit When the matrix 10 is to be operated to close the switch 12 or cross-point representing 19, an energizing signal is applied to the row conductor 24 and the column conductor 26. This results in the concurrent energization of the two coils 20 and 22. The magnetic field resulting from the energization of these two coils moves the overlapping ends 14a and 16a of the magnetic elements 14 and 16 in the indicated switch 12 into engagement to complete a conductive circuit therethrough. Since only a single one of the coils 20 or 22 on the remaining sealed switches 12 in the matrix circuit 10 is energized, the remaining sealed switches 12 are operated to a closed condition.

When the operated switch 12 representing the crosspoint 19 is released by terminating the energization of the coils 20 and 22, the overlapping ends 14a and 16a of the magnetic elements 14 and 16 in the switchseparate due to the resilience of these elements and tend to oscillate about their normal positions. If either of the coils 20 and 22 is reenergized during this period of oscillation, the switch 12 can be returned to an operated state to provide a false or inadvertent operation of the matrix circuit 18. To prevent this oscillation of the reeds 14 and 16 and the consequent possibility of a false operation of the switching matrix 10, the glass housing 18 of each of the sealed switches 12 in the matrix 10 is provided with a pair of axially spaced depressions or projecting portions 28 and 30 which are formed integral with the housing 18 and which engage the outer surfaces of the end portions 14a and 16a of the reeds 14 and 16 when the reeds 14 and 16 are in their normal or released position. Thus, when the magnetic elements 14 and 16 are released by terminating the energization of both of the coils 20 and 22, the resilience of these reeds separates the overlapping end portions 14a and 16a, and these portions move into engagement with the depressions 28 and 30. The impact of the reeds 14 and 16 on the depressions or projecting portions 28 and 30 dissipates the kinetic energy of the magnetic elements and prevents oscillation.

FIGURES 35 of the drawings illustrate a novel method of forming the depressions or projecting portions 28 and 39 in the glass housing 18 of the sealed switch 12. FIG. 3 of the drawings illustrates a conventional sealed switch in which the magnetic reeds or elements 14 and 16 are sealed in the opposite ends of the elongated glass or dielectric housing 18. This housing has a generally cylindrical or tubular form except at the ends where the seals for the magnetic reeds 14 and 16 have been formed. The sealed switch 12 can be formed in any of the well known methods such as those described in detail in United States Patents Nos. 2,697,307; 2,882,648; 2,984,046; and 3,061,144. The glass forming the housing 18 is substantially transparent to infra-red radiation, and the pressure within the sealed housing 18 is below atmospheric pressure due to the cooling of the gas sealed within the housing 18 during the formation of the switch 12. In the form illustrated in FIG. 3, the switch 12 is subject to oscillation of the free ends 14a and 16a of the magnetic elements 14 and 16 which can lead to false operation when the switch 12 is used in a matrix circuit, such as the circuit 10 illustrated in FIG. 1.

When the depressions 28 and 30 are to be formed in the sealed switch 12, a heat absorbing body or dot of heat absorbing material 32 (FIG. 4) is applied to the outer surface of the housing 18 aligned with one or both of the free ends of the magnetic elements. In one type of sealed switch constructed in accordance with the present invention, it has been found to be desirable to have the depressions 28 and 30 engage the end portions 14a and 16a around one-quarter of one inch from the end of the element. The body or bodies of heat absorbing material 32 can comprise a material that absorbs infra-redenergy, such as Acquadag which is a conductive colloidal graphite dispersion in water. The body 32 can comprise a dot having a diameter of about one-eighth of an inch. The switch 12 is preferably oriented so that the body of material 32 is disposed in vertical alignment directly above the planar surface of the end portion 14a to be engaged by the depression or projecting portion 28.

The switch 12 or, more particularly, the portion of the housing 18 on which the body of material 32 is disposed is then subjected to heat or infra-red radiation which softens or renders plastic the portion of the glass housing 18 engaged by or immediately adjacent the body 32 of heat absorbing material. As illustrated. in FIG. 5 of the drawings, the heating means or source of infra-red radiation can comprise a heater coil 34 connected to a source 36 of electric energy. A curved reflector 38 formed of a refractory material, such as molybdenum, is disposed above the heated coil 34 to focus the energy emitted from this coil on the body 32 of heat absorbing material. The heater coil 34 can comprise four turns of .05 inch diameter platinum alloy wire having an inside diameter of approximately a quarter of an inch. The lower end of the coil is disposed around one-sixteenth of an inch above the surface of the glass housing 18 immediately adjacent the body 32 of heat absorbing material.

When the heater coil 34 is energized with an alternating current potential from the source 36, this coil becomes incandescent or glows and emits radiations in the infra-red range of the spectrum. The glass of the housing 18 is substantially transparent to this radiation and does not become heated. However, the body of material 32 absorbs energy in the infra-red range and applies heat to the immediately adjacent area of the housing 18. As this portion of the housing 18 becomes softened or plastic, the force of gravity acting on the softened mass of glass and the pressure differential across the wall of the housing 18 resulting from the subatmospheric pressure within the housing 18 causes the softened glass to droop or be displaced inwardly toward the end portions 14a or 16a of the magnetic reeds 14 and 16. The application of heat from the coil 34 is continued until such time as sufficient heat has been imparted to the body 32 of material to soften the glass to the extent that it contacts the planar surface of the end portion 14a or 16a.

The physical engagement of the end portion 14a of the softened portion of the glass 18 terminates the sagging or movement of the softened glass without causing any displacement of the reeds 14 and 16 which might alter the gap between the end portions 14a and 16a and, thus, alter the operating characteristics of the sealed switch 12. In addition, the magnetic material forming the elements 14 and 16 has a good heat transmitting characteristic and serves as a heat sink to remove heat from the softened glass. This tends to solidify the glass and prevent any further movement of the softened portions thereof. The housing 18 of the switch 12 is then cooled to harden the plastic portion of the housing 18 to form the dimples or depressions 28 and 30. This cooling normally takes place quickly enough in the atmosphere. The body of material 32 can be removed by any suitable means, such as cleaning in an ultrasonic bath.

The depressions 28 and 30 can be formed in the housing 18 of the switch 12 by first applying the material 32 in a portion adjacent the inner end 140 of the magnetic element 14, applying heat to the switch 12, and then applying the material 32 for the depression 30 followed by a second heating step. This method has the advantage that the material 32 can be disposed above the inner ends 14a and 16a during the separate heating steps to permit the force of gravity to aid in the movement of the plastic or softened glass forming the depressions or projections 28 and 30. Alternatively, the material 32 can be applied adjacent both of the inner ends 14a and 16a, and heat is applied only once using a pair of the heating means 34. In this latter alternative, the pressure differential across the wall of the housing 18 provides the primary force for displacing the softened glass to concurrently form the two depressions 28 and 30.

The switching matrix 10 embodying the present invention is capable of operation at higher speeds by virtue of the means included therein for damping oscillatory movement of the magnetic elements or reeds 14 and 16, and this improvement in the speed of operation is achieved without increasing the size or power consumption of the switch 12 and without substantially increasing the cost thereof. In the switching matrix circuits 10 constructed in accordance with the present invention, the ten to fifty millisecond waiting period previously required for reapplying single operating signals to the circuit 10 has been reduced to a period on the order of one-quarter of one millisecond. In addition, the formation of the damping means 28 and 30 in the sealed switches 12 is accomplished in accordance with the present invention by a method which insures the application of heat to the glass housing 18 in only the areas in which the damping means or depressions 28 and 30 are to be formed and without disturbing the operating characteristics of the switch 12 or the gap between the overlapping ends 14a and 16a of the magnetic elements 14 and 16.

Although the present invention has been described with reference to a single illustrative embodiment thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, that will fall within the spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. A method of making sealed switches of the type having a sealed dielectric housing in the opposite ends of which a pair of magnetic elements are sealed with the inner ends of the magnetic elements disposed in spaced and overlapping relation, the internal pressure sealed within the housing being less than the external pressure to which the housing is subjected, which method comprises the steps of placing a body of heat absorbing material on the housing adjacent the end of one of the elements, and applying heat to the sealed switch to be absorbed by the material to heat the adjacent portion of the housing until the heated portion of the housing becomes sufficiently softened to be moved inwardly to a position adjacent the end of the magnetic element by the diiferential between the internal and external pressuresv 2. A method of forming inwardly extending projections in a glass housing of a sealed switch containing at least two magnetic elements, the internal pressure sealed within the housing being less than the external pressure to which the housing is subjected, which method comprises the steps of applying separate bodies of heat absorbing material to the glass housing adjacent each of the magnetic elements, applying heat to the switch to be absorbed by the bodies of material until the heat absorbed by the material renders only the portions of the glass housing adjacent the bodies of material plastic so that these plastic portions of the glass housing flow inwardly into the housing under the force of the differential between the internal and external pressures to form projections adjacent the magnetic elements, and cooling the switch to solidify the inwardly extending projections.

3. A method of selectively forming an inwardly ex tending projection in the glass housing of a sealed switch containing at least one magnetic element, said glass housing being substantially transparent to radiation in the infra-red range, the internal pressure sealed within the housing being less than the external pressure to which the housing is subjected, which method comprises the steps of placing a body of material that absorbs energy in the infra-red range on the glass housing in the location in which the projection is to be formed, applying infra-red energy to the glass housing to soften the glass in the housing adjacent the body of material so that the softened 7 glass of the housing is displaced inwardly under the force of the differential between the internal and the external pressures to form the projection, and solidifying the softened glass of the projection.

-4. A method of making sealed switches of the type having a sealed dielectric housing in the opposite ends of which a pair of magnetic elements are sealed with the inner ends of the magnetic elements disposed in spaced and overlapping relation, the internal pressure sealed within the housing being less than the external pressure to which the housing is subjected, which method com prises the steps of applying a body of heat absorbing material to the housing in alignment with an end portion of one of the magnetic elements, applying radiant heat to the material to heat the portion of the housing adjacent the material to a plastic state, terminating the application of heat only after sufficient heat has been absorbed by the material to permit the plastic portion of the housing to deform to a position adjacent the aligned end portion of the magnetic element under the force of the differential between the internal and external pressures, and cooling the plastic portion of the housing to retain the deformed portion in a position adjacent the end portion of the magnetic element under the force of the differential between the internal and external pressures, and cooling the plastic portion of the housing to retain the deformed portion in a position adjacent the end portion of the magnetic terminal.

5. A method of making a sealed switch of the type having a glass housing with a pair of magnetic elements sealed in the opposite ends of the housing so that their inner end portions are disposed in spaced and overlapped relation, the interior of said housing being at least somewhat below atmospheric pressure, which method comprises the steps of applying heat absorbing material to an area on the glass housing aligned with one of the inner end portions of the magnetic elements, applying heat to the switch in proximity to the material until the heat absorbed by the material places the portion of the glass adjacent the material in a plastic state, the plastic portion of the glass housing being displaced into the housing at least in part by the subatmospheric pressure within the housing to form an inwardly directed projection adjacent the end portion of the magnetic element, and cooling the plastic portion of the glass housing to retain the projection in the desired position.

6. A method of making a sealed switch of the type having a glass housing with a pair of magnetic elements sealed in the opposite ends of the housing so that their inner end portions are disposed in spaced and overlapped relation, the glass of said housing being substantially transparent to radiation in the infra-red range, the internal pressure sealed within the housing being less than the external pressure to which the housing is subjected,'which method comprises the steps of placing a body of'material that absorbs energy from infra-red radiation on the glass housing adjacent a selected point on one of the magnetic elements that is to be engaged by the glass of the housing, applying infra-red radiation to the switch at least in the area occupied by the body of material, said body of material absorbing energy from the applied radiation to render the adjacent portion of the glass housing plastic, and sustaining the application of infra-red radiation for a length of time sufficient to permit the plastic portion of the glass housing to move into engagement with the selected point on the one magnetic element under the force of the differential between the internal and external pressures.

7. The method set forth in claim 6 including the step of removing the body of material from the glass housing.

8. The method set forth in claim 6 including the step of repeating the steps set forth in claim 6 with the body of material being placed on the glass housing adjacent a selected point on the other magnetic element that is to be engaged by the glass of the housing.

Q A method of selectively forming an inwardly extending projection in the glass housing of a sealed switch containing at least one magnetic element, said glass housing being substantially transparent to radiation in the infrared range, the internal pressure sealed within the housing being less than the external pressure to which the housing is subjected, which method comprises the steps of placing a body of material that absorbs energy in the infra-red range on the glass housing in the location in which the projection is to be formed, applying infrared energy to the glass housing to soften the glass in the housing adjacent the body of material so that the softened glass of the housing is displaced inwardly under the force of the differential between the internal and external pressures to form the projection, terminating the application of the infra-red energy only after suflicient energy has been absorbed by the body of material to permit the softened glass in the projection to contact the magnetic element, said magnetic element serving as a heat sink to remove heat from the softened glass, and completing the cooling of the softened glass to solidify the projection in a position engaging the magnetic element.

References Cited -UNITED STATES PATENTS 12/1948 Ferrell -55 2/1959 Marini 65-23 

